<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        html,body,#parent{
            height:100%;
        }
        #parent > div {
            border: 1px solid #000;
        }
        #parent {
            display: flex;
            flex-direction: column;
        }
        #top {
            height: 100px;
        }
        #bottom {
            height: 50px;
        }
        #middle {
            flex: 1;
            display: flex;
        }
        #left {
            width: 200px;
        }
        #right {
            flex: 1;
            overflow: auto;
        }


        /*作者：sweet_KK*/
        /*链接：https://juejin.im/post/5aa252ac518825558001d5de*/
                                   /*来源：掘金*/
                                   /*著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。*/
    </style>
</head>
<body>
<div id="parent">
    <div id="top">top</div>
    <div id="middle">
        <div id="left">

            left
            <div style="background: blue; height: 1200px">

            </div>

        </div>
        <div id="right">right</div>
    </div>
    <div id="bottom">bottom</div>
</div>


</body>
</html>